Prior art space-borne communication systems consist of satellite vehicles which form the space segment and terrestrial components which form the ground segment to facilitate communications from any near-earth position to any other near-earth position. In a typical communication scenario, messages which can be data and/or voice are sent from the initiating near-earth user, possibly via an intervening space link, through a ground station to the space segment, then through multiple elements in the space segment, and finally back to earth via a second ground station, and ultimately routed to the terminating near-earth user. For this method to work reliably, it is critical that at least one route through the space segment be operational and that the terminating space-to-ground links, facilitated by the ground station, be operational. Failure to provide at least one route through the space segment or a failure in any of the terminating space-to-ground links will result in a lack of connectivity to portions of the globe.
Within prior art system design, connectivity to an entire terrestrial service area depends on the viability of the active space/ground link supported by the ground station. Any failure within that link will result in system outages. Additionally, prior art approaches to solving this problem are overly complex, requiring active coordination of multiple system components directed by a central control authority.
Within multiple satellite communication systems which employ constellations of orbiting satellites, either due to early constellation population considerations or satellite failures, "holes" can exist. When one of these holes covers a ground station area, connectivity to that area is lost.
Existing system design limits the positioning of ground stations such that a limited number of ground stations may be placed within the "footprint" of a single satellite, due to the satellite's limited resources (i.e., antennae) with which to implement space-to-ground links. Also, constellation traffic into or out of a single ground station is limited by the capacity of the supported space/ground link. This forces large cost and complexity increases as the traffic volume increases. Further, existing systems are limited in their ability to efficiently optimize operation for cost-per-packet considerations. These factors are not taken into account when data is transported.
Additionally, global communication does not occur in a equally distributed fashion about the globe, either in space or time. Most often, the volume of traffic expected in a communication system in any part of the world is highly dependent on the time of day and the day of the week, resulting in periods of relatively low activity and other periods of intense activity. Current global system designs exhibit throughput limitations or "bottlenecks" caused by this characteristic unbalanced system loading. Unfortunately, prior art satellite networks are somewhat limited in their ability to alleviate congestion situations without the invention. This forces the system designers to choose between specifying a system which is capable of handling peak loads, leaving excess network capacity un-utilized over large periods of time, or designing a limited system which is unable to support peak demand.
Therefore, there is a substantial need to provide a method and suitable apparatus for maintaining continuity of service in a global communication system despite interruptions in the satellite-to-ground radio frequency communication links.
There is also a substantial need to provide such a method and apparatus which can minimize the effect of substantial changes in the system network while still providing the necessary continuity of service.